The present invention relates to a cluster type multistage rolling mill, and particularly, to a cluster type split housing type rolling mill in which a housing containing a group of rolls is split into a top inner housing containing the upper half of the group of rolls and a bottom inner housing containing the lower half of the group of rolls, and the top and the bottom inner housings are contained in outer housings of an operating side and a driving side.
In recent years, users"" requirements for properties of plate materials manufactured by rolling of various kinds of materials have become increasingly severe, and it is required to control the plate thickness to a high degree of accuracy. A 20-stage rolling mill of an integral mono-block type having been widely used is good in accuracy of plate thickness because of the small deflection in work roll and the high rigidity of mill. However, because the gap of work rolls is small due to the geometric dimensional relationship caused by the integral housing, there are disadvantages in that it is difficult to perform plate passing work and that it is difficult to remove plate cobbles when rolled material rupture accident occurs. In order to solve these problems of the 20-stage rolling mill of an integral housing type, there has been provided a cluster type split housing type rolling mill in which a housing containing a group of rolls is split into a top inner housing containing the upper half of the group of rolls and a bottom inner housing containing the lower half of the group of rolls, and the top and the bottom inner housings are contained in outer housings of an operating side and a driving side. For example, a rolling mill of such a kind is disclosed in Japanese Patent Publication No. 50-24902. The rolling mill has a structure capable of increasing the work roll gap. Further, a cluster type split housing type rolling mill having the similar structure is also provided abroad, as described, for example, in SYMPOSIUM ON PRODUCTION TECHNOLOGY, 1993. In the rolling mill, the top and the bottom inner housings are equally split, and the top inner housing is supported by the operating side and the driving side outer housings each at two points.
However, the conventional cluster type split housing type rolling mills have a disadvantage in that the mill rigidity is too low to decrease the plate thickness accurately because the housing is split.
That is, in the cluster type split housing type rolling mill disclosed in Japanese Patent Publication No.50-24902, the top and the bottom inner housings are equally split, and the upper sides of the top inner housing are supported by the operating side and the driving side outer housings each at one central point through pass line adjusting mechanisms, and the lower sides of the bottom inner housing are supported by the operating side and the driving side outer housings each at one central point through pressing-down cylinders. Therefore, the top and the bottom inner housings are easily deformed in the horizontal direction to cause bore opening in the housings by the horizontal component (horizontal load) of the milling reaction force acting through four backing bearings arranged in the top and lower both sides. The bore opening horizontally moves the backing bearings to cause detaching of the top and the lower work rolls from the plate. Therefore, the cluster type split housing type rolling mill exhibits mill rigidity which is too low to decrease the plate thickness accurately.
In the cluster type split housing type rolling mill described in SYMPOSIUM ON PRODUCTION TECHNOLOGY, 1993, although the upper side of the top inner housing is supported by the operating side and the driving side outer housings each at the two points, it is the same as the rolling mill disclosed in Japanese Patent Publication No. 50-24902 that the top and the bottom inner housings are equally split and that the lower side of the bottom inner housing is supported by the operating side and the driving side outer housings each at one point. Therefore, there is a problem in that the mill rigidity is decreased due to the large bore opening.
As described above, in the conventional cluster type split housing type rolling mills, optimizing design in regard to the mill rigidity due to the bore opening is not performed.
An object of the present invention is to provide a cluster type split housing type rolling mill which controls plate thickness by increasing mill rigidity.
(1) In order to attain the above-mentioned object, a cluster type multistage rolling mill in accordance with the present invention is a cluster type multistage rolling mill comprising a top inner housing for containing a group of rolls arranged above a pass line; a bottom inner housing for containing a group of rolls arranged below the pass line; and operating side and driving side outer housings for containing the top and said bottom inner housings, which comprises a top side supporting means for supporting the upper side of the top inner housing to the outer housings in the operating side and the driving side each at two points in the front side and in the back side with respect to a pass direction, the top side supporting means being arranged in the upper side of the top inner housing and between the operating side and the driving side outer housings; and a bottom side supporting means for supporting the lower side of the bottom inner housing to the outer housings in the operating side and the driving side each at two points in the front side and in the back side with respect to the pass direction, the bottom side supporting means being arranged in the lower side of the bottom inner housing and between the operating side and the driving side outer housings.
By supporting the top and bottom inner housings in the both sides of the operating side and the driving side each at two points not at one point, as described above, the displacements of backing bearings in the both sides of the top and the bottom sides caused by the components of rolling load can be made small, and reduction of the mill rigidity can be suppressed. Therefore, rolling stable and good in plate thickness control capability can be performed.
(2) Further, in order to attain the above-mentioned object, a cluster type multistage rolling mill in accordance with the present invention is a cluster type multistage rolling mill comprising a top inner housing for containing a group of rolls arranged above a pass line; a bottom inner housing for containing a group of rolls arranged below the pass line; and operating side and driving side outer housings for containing the top and the bottom inner housings, which comprises a top side supporting means for supporting the upper side of the top inner housing to the outer housings in the operating side and the driving side each at two points in the front side and in the back side with respect to a pass direction, the top side supporting means being arranged in the upper side of the top inner housing and between the operating side and the driving side outer housings; and a bottom side supporting means for supporting the lower side of the bottom inner housing to the outer housings in the operating side and the driving side each at one point in the middle with respect to the pass direction, the bottom side supporting means being arranged in the lower side of the bottom inner housing and between the operating side and the driving side outer housings, wherein when a vertical rigidity ratio between the top and the bottom inner housings is defined as a rigidity of the top inner housing/a rigidity of the bottom inner housing, the housing proportion is formed so that the vertical rigidity ratio may become a value within a range of 1.02 to 1.18.
By supporting the top inner housing in the both sides of the operating side and the driving side each at two points not at one point, as described above, the displacements of backing bearings in the both sides caused by the components of rolling load can be made small, and reduction of the mill rigidity can be suppressed. Further, by setting the vertical rigidity ratio between the top and the bottom inner housings to a value within the range of 1.02 to 1.18 on the premise of the above, the total rigidity of the top and the bottom inner housings can be increased compared to that in a case where the vertical rigidity ratio between the top and the bottom inner housings is 1 (one), and as the result, reduction of the rigidity of the top and the bottom inner housings can be suppressed. Therefore, rolling stable and good in plate thickness control capability can be performed.
(3) Further, in order to attain the above-mentioned object, a cluster type multistage rolling mill in accordance with the present invention is a cluster type multistage rolling mill comprising a top inner housing for containing a group of rolls arranged above a pass line; a bottom inner housing for containing a group of rolls arranged below the pass line; and operating side and driving side outer housings for containing the top and the bottom inner housings, which comprises a top side supporting means for supporting the upper side of the top inner housing to the outer housings in the operating side and the driving side each at two points in the front side and in the back side with respect to a pass direction, the top side supporting means being arranged in the upper side of the top inner housing and between the operating side and the driving side outer housings; and a bottom side supporting means for supporting the lower side of the bottom inner housing to the outer housings in the operating side and the driving side each at one point in the middle with respect to the pass direction, the bottom side supporting means being arranged in the lower side of the bottom inner housing and between the operating side and the driving side outer housings, wherein a height of the bottom inner housing is higher than a height of the top inner housing.
By supporting the top inner housing in the both sides of the operating side and the driving side each at two points not at one point, as described above, the displacements of backing bearings in the both sides caused by the components of rolling load can be made small, and reduction of the mill rigidity can be suppressed. Further, by forming the height of the bottom inner housing higher than the height of the top inner housing on the premise of the above, the total rigidity of the top and the bottom inner housings can be increased compared to that in a case where the heights of the top and the bottom inner housings are equal to each other. Therefore, rolling stable and good in plate thickness control capability can be performed.
(4) In the above item (3), it is preferable that a height ratio of the top inner housing to the bottom inner housing is within a range of 0.72 to 0.98.
By doing so, the vertical rigidity ratio between the top and the bottom inner housings becomes a value within a range of 1.02 to 1.18. Therefore, rolling stable and good in plate thickness control capability can be performed.
(5) Further, in order to attain the above-mentioned object, a cluster type multistage rolling mill in accordance with the present invention is a cluster type multistage rolling mill comprising a top inner housing for containing a group of rolls arranged above a pass line; a bottom inner housing for containing a group of rolls arranged below the pass line; and operating side and driving side outer housings for containing the top and the bottom inner housings, Which comprises a top side supporting means for supporting the upper side of the top inner housing to the outer housings in the operating side and the driving side each at two Points in the front side and in the back side with respect to a pass direction, the top side supporting means being arranged in the upper side of the top inner housing and between the operating side and the driving side outer housings; and a bottom side supporting means for supporting the lower side of the bottom inner housing to the outer housings in the operating side and the driving side each at one Point in the middle with respect to the pass direction, the bottom side supporting means being arranged in the lower side of the bottom inner housing and between the operating side and the driving side outer housings, wherein a width in the pass direction of the bottom inner housing is wider than a width in the pass direction of the top inner housing.
By supporting the top inner housing in the both sides of the operating side and the driving side each at two points not at one point, as described above, the displacements of backing bearings in the both sides caused by the components of rolling load can be made small, and reduction of the mill rigidity can be suppressed. Further, by forming the width of the bottom inner housing wider than the width of the top inner housing on the premise of the above, the total rigidity of the top and the bottom inner housings can be increased compared to that in a case where the widths of the top and the bottom inner housings are equal to each other. Therefore, rolling stable and good in plate thickness control capability can be performed.
(6) In the above item (5), it is preferable that a width ratio of the top inner housing to the bottom inner housing is within a range of 0.72 to 0.98.
By doing so, the vertical rigidity ratio between the top and the bottom inner housings becomes a value within a range of 1.02 to 1.18. Therefore, rolling stable and good in plate thickness control capability can be performed.